Controlling the maturity of the grapes remains the cornerstone of the winegrower’s work. It is a question of determining the optimal date for harvesting according to several parameters: physiological maturity, balance between alcohol and acidity, phenolic maturity, quality of the colouring matter, and tannins. The ripeness of the grapes is the sine qua non condition of a successful wine. A good maturity favours a more pronounced colour and ripe fruit aromas. Harvesting too early results in unripe grapes and wines which tend to show vegetal, herbaceous notes.